Yeah, that's going to change things quite a bit. It just so happens astrophotography is something i'm starting to get into and this post is very timely. Have you thought about getting a tracking mount? What do they cost anyway? Would you be better off with that money going towards that instead of a lens?

Okay, to clarify what I need this for, I want to do some wide field astrophotography, so the wider the better. I'm probably looking more for an equivalent 28mm rather than an actual 28mm, which means around 17mm or so actual focal length.

I think I can do that pretty nicely with my 15-85mm when pulled to its widest, but it's still fairly slow, and without an equatorial mount I'm risking star trails (which, admittedly, isn't much of a concern at this short focal length, but still a concern). The 50mm is fast enough, but is probably a little tight on the FOV for what I need since I only have a crop sensor camera.

On that note, any idea how focal length translates into FOV in the photo? The Andromeda galaxy, for example is about 2 degrees wide, and I think 85mm's FOV is about 15 degrees on a full frame, so I can probably capture Andromeda nicely on my lens and crop it, provided I have an equatorial mount.

For fast, wide and relatively cheap, the two contenders are Samyang 14mm f/2.8 and Tokina 11-16mm f/2.8. Other options are either above 17mm, slower than f/2.8 or much more expensive

For fast, wide and relatively cheap, the two contenders are Samyang 14mm f/2.8 and Tokina 11-16mm f/2.8. Other options are either above 17mm, slower than f/2.8 or much more expensive

Yep, and both would work well for your purposes. The Tokina would give you more options, the Samyang would be cheaper. If those aren't fast enough, your only real Canon option is the 28mm f/1.8. Also, if the Tokina is too wide for your tastes, there is the older Canon 20-35mm f/2.8L that you can get for $4-500ish on Ebay, if not cheaper. But I think the 28mm f/1.8 would probably give you stronger image than that.

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fester

I discovered this little gadget in my internet wanderings; you might find it interesting. It is an equatorial motorized camera mount. I have no experience with this, only saved the link for future reference. May allow you to buy a cheaper lens and keep the star trails at bay.

I'm going to look into that also, thanks. That was sort of the point of my post. With a tracking system you can use slower less expensive lenses. Besides i've yet to come across a lens that was best for astro work wide open. including the ef200mm1.8

For that price you could get a computerized CG5 mount. I use a Tokina 11-16 for widefield astro and find it suitable for timelapse but unfit for single images unless stopped to f4 or slower. With a tracking mount lens speed is not so critical but resolution always matters. A 300/4 or 400/5.6 works well for many astro objects at 1600ISO for 30-90 seconds. 3200 on the 18MP sensors with less shutter time.

For fast, wide and relatively cheap, the two contenders are Samyang 14mm f/2.8 and Tokina 11-16mm f/2.8. Other options are either above 17mm, slower than f/2.8 or much more expensive

Yep, and both would work well for your purposes. The Tokina would give you more options, the Samyang would be cheaper. If those aren't fast enough, your only real Canon option is the 28mm f/1.8. Also, if the Tokina is too wide for your tastes, there is the older Canon 20-35mm f/2.8L that you can get for $4-500ish on Ebay, if not cheaper. But I think the 28mm f/1.8 would probably give you stronger image than that.

+1 for the EF 28mm f/1.8. It's great for landscapes, but it's fast enough for indoor use. It's also small and light (but the build is solid, like the 85mm f/1.8 ), so it's easy to take along when shooting mainly with another lens.

+1 for the EF 28mm f/1.8. It's great for landscapes, but it's fast enough for indoor use. It's also small and light (but the build is solid, like the 85mm f/1.8 ), so it's easy to take along when shooting mainly with another lens.

The OP is shooting with APS-C and wants a wide angle lens. 28mm on APS-C is not wide angle.

Astrophotography (like anything else, especially photography-related) can be as expensive as you want.

There are several options for tracking equatorial mounts. First, there are the full computerized German eq. mounts made for telescopes. These are probably the best option, because they are intended for exactly this purpose, although they're probably more intended for use with an actual telescope and astronomy CCD camera. I've never seen one that's a good out-of-the-box DSLR astrophotography mount. The other option is a simple motorized eq. mount. They don't have the computer thing ("GoTo", etc.) that automatically points the mount at specific objects, but they do have the motors that allow the mount to track with the stars (sidereal) or sun or moon.

EDIT: Looking closer at Vixen's site, I found they have what seems to be a decent mount for astrophotography. GP2 Photo Guider ~$1100, should work out-of-the-box.

The third option, which I have started out with, is the Astrotrac system. My kit is mostly made from standard photography tripod components, rather than the Astrotrac pier/wedge system. I have the Manfrotto 055XPROB tripod, along with the 410 geared head (serves as the equatorial mount for precise polar alignment), the Astrotrac itself, and a ball head on top of that. The Astrotrac, once properly aligned, uses a worm gear to rotate its top half at the same rate as the stars, so the ball head, no matter where it's pointed, will track with the stars. It's fairly precise, especially for wide angle sky shots, and it's even possible to take longer focal length shots for up to a few minutes exposure. Take a look at my setup on Flickr.

I went with the Astrotrac because it's mostly manual, very educational, and when I'm not doing astrophotography, I still have a very good tripod and photographic tripod heads to use. That geared head is fantastic for landscapes. All of the components considered, I probably spent about as much as I would have with a special motorized eq mount, but the versatility is an added benefit.

The other thing you should consider is a light pollution suppression filter. This is the next component on my list. These filters are specifically designed to cut down on the most common city lights (sodium vapor, etc) without restricting the light you want from the stars. Astronomik probably makes the best filters, and they even have filters that clip into the lens mount on your camera (assuming you have a Canon crop sensor camera). Look at either their CLS or UHC filters. OPT is a good place to find them in the USA.

Getting back to your original question... Lens wise, if you get a good tracking system, your choice of lens doesn't matter as much, especially the aperture. For sharpness, you're probably going to want to stop the lens down a bit anyways. It's very hard to focus precisely (even at infinity) on a dark sky, so it's best to go with something around f/8-f/11 and take longer exposures. If you want something really wide, and it sounds like you're on a crop camera, I recommend the EF-S 10-22. It's a great lens, solid construction, and very wide - 16-35mm equivalent. It costs $800 at B&H. Apart from that, your 15-85mm should do a fine job for you. (Very important, though - remember to turn off your stabilizer when it's on a tripod.)

The technique the professionals use is to take lots of medium-length exposures (2-5 minutes) and stack them using software like Deep Sky Stacker (free program). I haven't used this program yet, but I'm going to. It aligns and combines several light frames (normal star photos) and dark frames (shutter or lens closed off) to cut down on sensor noise.

If you want something really wide, and it sounds like you're on a crop camera, I recommend the EF-S 10-22. It's a great lens, solid construction, and very wide - 16-35mm equivalent.

I thought about recommending this lens as well, as I've used it some for astrophotography. The one thing I would also recommend is that all of your RAW photos taken with this lens should be processed with Canon's Digital Photo Professional or by Lightroom 4 to reduce chromatic aberration in the corners. DPP seems to handle chromatic aberration reduction really well on the 10-22, followed by LR4. IMO, Apple Aperture has terrible chromatic aberration correction for this lens. Other than that, it's a fine lens for capturing wide swaths of sky.

+1 for the EF 28mm f/1.8. It's great for landscapes, but it's fast enough for indoor use. It's also small and light (but the build is solid, like the 85mm f/1.8 ), so it's easy to take along when shooting mainly with another lens.

The OP is shooting with APS-C and wants a wide angle lens. 28mm on APS-C is not wide angle.

Actually, the OP states he wants something wider than 50mm ("the 50mm is too tight"), preferably "faster than f/2," and specifically mentions the Canon 28mm f/1.8 USM, but was unsure about it. Therefore, recommending the 28mm f/1.8 was completely reasonable.

Actually, the OP states he wants something wider than 50mm ("the 50mm is too tight"), preferably "faster than f/2," and specifically mentions the Canon 28mm f/1.8 USM, but was unsure about it. Therefore, recommending the 28mm f/1.8 was completely reasonable.

OP writes:

"Okay, to clarify what I need this for, I want to do some wide field astrophotography, so the wider the better. I'm probably looking more for an equivalent 28mm rather than an actual 28mm, which means around 17mm or so actual focal length."

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locke42

Actually, the OP states he wants something wider than 50mm ("the 50mm is too tight"), preferably "faster than f/2," and specifically mentions the Canon 28mm f/1.8 USM, but was unsure about it. Therefore, recommending the 28mm f/1.8 was completely reasonable.

OP writes:

"Okay, to clarify what I need this for, I want to do some wide field astrophotography, so the wider the better. I'm probably looking more for an equivalent 28mm rather than an actual 28mm, which means around 17mm or so actual focal length."

Grrr, still not notifying me.

Okay, I see my followup post has introduced a little bit of confusion.

First, I do want a fast wide-angle lens for astrophotography. I got my camera with the intention of eventually using it for astrophotography. (In fact, I was on the verge of getting the 60Da, but the price difference was just too much.) My 15-85mm covers the focal length, but not the speed. Of course, I wouldn't mind one that goes even wider than 15mm, as long as it's still fast. For this I'd prefer a zoom.

Second, I also want a possible replacement/complement to my current 50mm f/1.4 lens. The 50mm, as I said, can sometimes be a bit too narrow for the indoors shots that I like to take. For THIS purpose, I'd like something with an actual focal length between 20mm and 40mm, either a prime or a zoom.

Anyway, I've been doing some research and Canon's 17-55mm f/2.8 seems to be the best compromise. It's not as fast as I'd like (I'd really love sub-f/2 like my 50mm prime), but I don't know if that's even possible with my other criteria.